This grant is composed of three separate projects with the following objectives: (1) The determination of the location in the collagen chains which are in intimate contact with the hydroxyapatite in bone. To do this we are exposing calcified bone to methyl vinyl ketone (MVK), removing the mineral, digesting the collagen with CNBr, separating the peptides, and analyzing them for the extent to which the lysyl residues have been derivatized by the MVK. The peptides which are less well derivatized are assumed to be in more intimate contact with the mineral phase. (2) We are attempting to carry out the chemical systhesis of the desmosines of elastin using the model peptides, poly(Lys-Ala2) and poly(Lys-Ala3). Oxidation of lysyl residues using NBS has been achieved in poly-L-lysine. Under the right conditions, we have isolated several crosslinks, including a crosslink with a 270 nm absorption maximum as in desmosines. (3) An investigation of the mechanism of the collagen: platelet interaction is in progress. We are determining the nature of both the collagen and platelet binding sites. BIBLIOGRAPHIC REFERENCE: F. Svec and H. B. Bensusan, Extent and Topography of the Acetylation of Calcified Chicken-Bone Collagen, Conn. Tissue Res. 3, 253 (1975).